Silicic films, which are relatively hard and dense, are used in various applications, specifically a hard-coat film, a gas barrier film and a reinforcement film for substrates and circuits and the like in the semiconductor manufacturing industry. Various silicic films for such applications have been investigated. Non-Patent Document 1 discloses a method for forming a SiON layer by coating polysilazane on a substrate, drying, and then irradiating with excimer laser (wavelength 172 nm) in an inert gas atmosphere. Patent Document 1 also discloses a method for forming a high-performance gas barrier film using a similar method. Thus, methods for high-performance silicic films have been investigated by using a composition having Si—N, Si—H and N—H bonds.
In particular, Patent Document 1 discloses a method of repeating manufacturing steps for forming film to obtain more stable film. However, the present inventors have found that density of the film may be insufficient when irradiation light is limited to 172 nm wavelength. Patent Document 2 also discloses a method for forming a siliceous film by coating polysilazane containing a catalyst on a substrate, drying, and then irradiating with vacuum ultraviolet (wavelength under 230 nm) and ultraviolet (wavelength 230-300 nm) simultaneously, tandemly or alternately in a water vapor atmosphere. However, there is still room for improvement in terms of density of the siliceous film.
Patent Document 3 also discloses that gas barrier performance is degraded in consequence of increased concentration of Si—O bonds in a formed film, which is irradiated with vacuum ultraviolet light in a high-oxygen atmosphere. According to this disclosure, a film having many Si—N bonds, not Si—O bonds, is considered to be preferred to achieve a high-performance gas barrier film.